The invention concerns an optical switch, and in particular a non-blocking free-space switch.
The tantalizing prospect of utilizing optical wiring in a Silicon-based electronic environment becomes ever more attractive as speed, complexity and integration density increase. Tremendous incentives are increasingly apparent for the development of optical and optoelectronic devices that are compatible with VLSI (Very Large Scale Integrated) Silicon (Si) technology. Large-area and low-cost Si wafer technology provides an ideal platform for photonic guided-wave devices. In addition, mature Si processing technology, micromachining techniques, Silicon-on-Insulator (SOI) and heteroepitaxy, can be used to fabricate complex optical structures such as micro-optical devices and hybrid optoelectronics. Compatibility with mainstream Si Integrated Circuit (IC) technology promises low cost and reliable manufacturing of monolithic Si-based optoelectronic integrated circuits that will be much like today""s electronic ICs.
Optical switches, very much like the conventional transistor, are essential components of photonic guided-wave devices. Optical switching is used for rearranging the optical paths in a telecommunication network, for example.
Most optical switches have one or more elements that are mechanically actuated. These kind of switches are thus referred to as optomechanical switches. Typical examples are addressed in xe2x80x9cCurrent European WDM deployment trendsxe2x80x9d, E. Lowe, IEEE Commun. Mag., Vol. 36, pp. 46-50, 1998, and in xe2x80x9cAll-silicon bistable micro mechanical fiber switchesxe2x80x9d, M. Hoffmann et al., Electron. Lett., Vol. 34, pp. 207-208, 1998.
It is desirable to have optical switches that are less bulky and more reliable than optomechanical switches. An often followed approach to build an Nxc3x97M optical switch is to cascade a (large) number of simple 2xc3x972 optical switching elements, where each of these 2xc3x972 switches consists of one or two tunable Mach-Zehnder interferometers. An example of such a switch is described in xe2x80x9cLow-Loss and High-Extinction-Ratio Silica-Based Strictly-Nonblockling 16xc3x9716 Thermooptic Matrix Switchxe2x80x9d, T. Goh, M. Yasu, K. Hattori, A. Himeno, M. Okuno and Y. Ohmori, IEEE Photonics Technology Letters, Vol. 10, No. 6, June 1998. A second approach, which uses beam-steering to realize a 1xc3x97N or Nxc3x971 switch is described in xe2x80x9cCompact Versatile Thermooptical Space Switch Based on Beam Steering by a Waveguide Arrayxe2x80x9d, E. Flxc3xcck et al., IEEE Photonics Techn. Lett., Vol. 11, No. 11, pp. 1399-1401, November 1999. This integrated optical switch is similar to an arrayed waveguide grating (AWG) wavelength multiplexer. It consists of a number of input waveguides, a star coupler that divides the input light over an array of channel waveguides and a second star coupler that refocuses the light from the array onto one of the output waveguides. The array waveguides at the input side are equipped with tunable lenses. By adjusting the phase distribution one can determine onto which output waveguide the light is focussed. This allows to switch input signals to desired output channels. This IEEE publication is herewith incorporated by reference.
It is an object of the invention to provide a switch which is simple and inexpensive to fabricate and which switches light paths rapidly and without frictional wear to the switch.
It is another object of the invention to provide a switch which can be integrated with other components, e.g., optical components, on a substrate.
The invention concerns optical switches and data transmission systems comprising one or more such switches. A switch, in accordance with the invention, comprises an input channel with an input optical free-space element, an intermediate optical free-space element, an input tunable optical lens with adjustable projection characteristic for projecting a lightwave received from the input optical free-space element into the intermediate optical free-space element. In addition, the switch comprises an output channel with an output optical free-space element, and an output tunable optical lens with adjustable reception characteristic for capturing the lightwave from the intermediate optical free-space element and for feeding the lightwave to the output optical free-space element.